Nitration of organic compounds



Oct. 6, 1953 w. H. MARSHALL, JR

NITRATION OF ORGANIC COMPOUNDS Original Filed April 2. 1948 INVENTOR. WALTON H. MARSHALL JR. BY 6.; M ,a 4 0M ATTORNEY.

Patented Oct. 6, 1953 UNITED STATES PATENT OFFICE NITRATION OF ORGANIC COMPOUNDS Walton H. Marshall, Jr., Bronxville, N. Y., as- Kellogg Company, Jersey signor to The M. W. City, N. J.,

a corporation of Delaware Original application April 2, 1948, Serial No.

18,607. Divided and this 1951, Serial No. 238,559

9 Claims. 1

This application is a division of application Serial No. 18,607, filed April 2, 1948.

This invention relates to an improved method for nitrating organic compounds. More particularly the invention relates to an improved method for nitrating hydrocarbons or mixtures of hydrocarbons, whether parafiinic, olefinic, acetylenic, aromatic, or naphthenic, and other organic compounds such as alcohols, aldehydes, acids, halogenated derivatives, etc. The hydrocarbons to which the improved process is particularly applicable are propane and benzene.

In the nitration of propane, vapors of nitric acid and propane are contacted at elevated temperature and pressure to bring about a reaction which results in the formation of nitroparafiins, with some alcohols, acids, etc., as oxidation byproducts. The reaction proceeds without the use of a catalyst in a temperature range of approximately 250 C. to 450 C. The pressure normally used is 200250 pounds per square inch. In this operation an important technical problem is presented by the necessity for vaporizing nitric acid. The hot nitric acid about to become vaporized is highly corrosive to metal surfaces. Vessels made of special cast iron alloys are capable of withstanding such corrosive conditions, but such vessels are quite brittle and susceptible to brealqage because of thermal shock. Such brittleness substantially precludes the use of relatively large evaporating vessels made of these materials.

It is an object of my invention to provide an improved process for nitrating organic compounds, according to which the nitric acid is vaporized without contact of the liquid acid with the walls of any metal container. It is a further object of my invention to provide an improved process in which the heat required to vaporize the nitric acid is supplied largely by the heat of the nitration reaction. Other objects of my invention are apparent from the following more detailed description.

In accordance with my improved process, the cool relatively non-corrosive liquid nitric acid is sprayed into a dense bed of finely divided suspended solids, not reactive with the hot acid, which are at a temperature such that the nitric acid vaporizes substantially instantaneously upon contact of the liquid with the hot solids. The vapors thus formed are substantially immediately contacted in the same zone with vapors of the organic compound to be nitrated.

The finely divided solid heat-containing material preferably is maintained as a substantially dense fluidized mass by the passage of aerating application July 25,

gases or vapors upwardly therethrough at a suitable velocity. However, the invention is not limited to an operation in which the solid heatcontaining material is maintained in this condition, but includes within its scope the step of vaporizing nitric acid by contacting the nitric acid liquid with hot finely divided solids under any condition of concentration or density in which the quantity of solids and the heat content thereof are sufiicient to effect the desired substantially instantaneous vaporization of the nitric acid.

Any suitable gas or vapor may be employed to agitate andsuspend a mass of hot solids, for example the nitric acid vapors formed by contact with the hot solids may serve as the aerating and agitating medium. However, it is preferable to employ the vapors of the organic compound to be nitrated. This provides more positive agitation of the mass of solids and facilitates prompt reaction of the nitric acid vapor with the organic compounds to be nitrated. Furthermore, this method of aerating the hot solids permits the use of heat contained therein to preheat the organic reactant. However, any other suitable gas or vapor may be employed to aerate or agitate the mass of solids.

It is preferable to maintain the hot solids in the vaporizing zone in a condition of high concentration and turbulence which is characteristic of masses of finely divided solids aerated by the passage of gas or vapor upwardly therethrough at relatively low linear velocity. The organic reactant also is introduced into the vaporizing zone and the heat of the resulting reaction of the nitric acid and the organic compound is largely absorbed by the aerated mass of solids. The heat of reaction absorbed by the solid particle from the reaction occurring on or adjacent to its surface is subsequently utilized for vaporizing the nitric acid when the solids particle is brought into contact with liquid nitric acid which is continuously introduced into the vaporizing zone. In accordance with this method of operation nitric acid may be vaporized out of contact with any metal surfaces subject to corrosion, and the reaction of the organic compound and nitric acid vapor in contact with the solid particles employed to effect vaporization effects the transfer of heat of reaction to the vaporizing step, thus providing the heat of vaporization and withdrawing the heat of reaction from the reaction zone.

The invention will be described in more detail by reference to the drawings, which illustrate tions in Fig. 1 and Fig. 2 have been indicated by the same reference numerals.

In the modification shown in Fig. 2, the liquid nitric acid may be introduced at one or more different elevations in the reactor through spray nozzles 33. By introducing the liquid acid at a plurality of such elevations the vaporization of the acid is distributed over a greater part of the reaction zone whereby the removal of the heat of reaction is more uniform. However, it may be advantageous to introduce all of the acid at any one of the four difierent elevations provided for in Fig. 2 whereby there is a substantial distance between the point of introduction of the vaporized hydrocarbons and the point of vaporization of the nitric acid.

The lines leading to the acid spray nozzles may be in contact, for substantial length therof, with the fluidized mass of hot solids, whereby the acid may tend to be heated during passage therethrough to a temperature which would cause substantial corrosion of the nozzle and connecting lines. To avoid this effect suitable means may be provided for cooling the acid line leading through the fluidized mass of solids to the exit nozzle. Such means are illustrated in Fig. 4 as applied to line 28 and nozzle 29. As shown in Fig. 4, that part of pipe 28 leading to nozzle 29 and in contact with hot catalyst may be enclosed within an outer cylindrical casing 34 which is closed at the end adjacent nozzle 29. Cooling liquid may be circulated adjacent pipe 28 inside casing 34. To provide for more positive circulation of such cooling liquid an internal cylindrical member 35, concentric with pipe 28 and member 34, may be provided. Thus a suitable cooling fluid may be circulated toward nozzle 29 through the annulus between pipe 23 and member 35, and back to the source of supply through the annulus between members 34 and 35. In this manner the nitric acid may be maintained at temperatures sufficiently low to prevent corrosion prior to its emergence from nozzle 29, or any other suitable distributor.

The nitric acid may be supplied to the reaction zone in any desired concentration or purity. In certain cases, where oxygenated derivatives are desired, N02 may be used as an oxygen carrier.

The nitric acid and reactants ordinarily are introduced into the reaction zone in a ratio which depends upon the reaction conditions and the nature of the materials used. In general, however, the quantity of hydrocarbon or organic reactant used is in excess of the stoichiometric amount which is necessary for the reaction. The following equation illustrates the nitration of propane, with respect to the relative molar quantities of reactants which are necessary for the reaction.

The finely divided solid which is primarily a heat transfer agent need not exert any catalytic action, although it may be desired to employ a material which has a catalytic effect on the reaction, depending upon the particular organic compound to be nitrated. The finely divided solid material may be of any particle size which permits it to be suspended or agitated or fluidized in the contact zone. Ordinarily material having a range of particle sizes falling entirely or largely within the range of to 500 microns may be employed with advantage. The linear velocity of the aerating gases in the contact zone and the particlesize ordinarily should be such that the solids shall be present in the contact zone in a density of 5 to 40 pounds per cubic foot. The invention is not limited to this condition, however, and it is operable under conditions in which the solid is present in the contact zone in lesser or greater density.

Any suitable, sufficiently inert, material may be employed as the finely divided contact material. Such materials may include sand, glass, and carbon, of the proper particle size, as well as nitrates which are stable under the conditions of operation, such as barium nitrate. Other materials having a catalytic effect may be substituted for the above-named contact materials, or the abovenamed contact materials may be impregnated, or otherwise associated, with small amounts of catalyst for the nitration reaction.

The temperature and pressure employed in the reaction zone ordinarily correspond to those employed in previous nitration processes, and depend upon the characteristics of the particular organic compound to be nitrated. For the nitration of paraifins the operating pressures range from atmospheric to approximately 500 pounds per square inch and temperatures range from 300 F. to 900 F. Similarly the reaction time and/or space velocity varies according to the particular reaction and the nature of the solid employed as the contact agent.

The modifications of the invention described above in connection with the drawing indicate the maintenance of a body of contact material in a contact chamber. The invention is not limited to such operations, however, and it may be desirable to introduce or withdraw solids from the contact vessel in any convenient manner in order to circulate the solids through other pieces of equipment in order to cool or heat the solids, or in order to regenerate catalytic activity.

The temperature of the reaction may be controlled in any convenient manner, such as by adjusting the temperature of the stream of organic compound fed to the reaction chamber, by controlling the ratio of recycling of unconverted reactants, and by heating or cooling the finely divided contact material, as by means of heating or cooling tubes in the contact chamber.

I claim:

1. In the process for reacting nitric acid with a hydrocarbon in the vapor phase to produce a nitrated hydrocarbon as the principal product, the method of operating the process to decrease the corrosive effects of liquid nitric acid which comprises contacting liquid nitric acid with a mass of finely divided solid material in a quantity and at a temperature sufficient to effect complete vaporization thereof, and then reacting the nitric acid vapor thus produced with the hydrocarbon reactant.

2. The method of claim 1 wherein the hydrocarbon is a paraflinic hydrocarbon.

3. The method of claim 1 wherein the hydrocarbon is propane.

4. The method of claim 1 wherein the hydrocarbon is benzene.

5. In the process for reacting nitric acid with a hydrocarbon in the vapor phase to produce a nitrated hydrocarbon as the principal product, the method of operating the process to decrease the corrosive efiects of liquid nitric acid and to utilize the heat of nitration for vaporizing the liquid nitric acid which comprises introducing liquid nitric acid into a hot mass of finely divided solid material in a quantity and at a temterm it 7, 1i: wpia l hi drbbdybdh to feast w th the nitiik; @631 m th vapor; phase, thus thje hat of initiation is ab sdrb'ed by the may divided solid material and is utilized for mai'fita'iniiig the desired r'a'ctioh tini t ez "1. In the pi-o'cess dr reat'in'g hitiidhbid with a hyd'rbcarbbn in the vapqiptiase 12b produce a 'I it'ratd hymfocarbon as the principal prdd'ubt, th'e' method of opx atir'fg the piocs's t6 dpi'is'e to utilize th helt of ummon fof maintaining the desired ractipn tempeiature \ivhih 66in p is'es immune-mg mum nitric, acid into a mas or hot finely dividd solid iha'trial in a quantity "memes ,7 v v fi-if rev-e1; the corrosive effects "Of liquid nitrid acid and tin IV-ALTON H. MARSHALL; Jii.

Bfei'nc's Cited in tile file or this patent tiixrriin STATES PATENTS 

1. IN THE PROCESS FOR REACTING NITRIC ACID WITH A HYDROCARBON IN THE VAPOR PHASE TO PRODUCE A NITRATED HYDROCARBON AS THE PRINCIPAL PRODUCT, THE METHOD OF OPERATING THE PROCESS TO DECREASE THE CORROSIVE EFFECTS OF LIQUID NITRIC ACID WHICH COMPRISES CONTACTING LIQUID NITRIC ACID WITH A MASS OF FINELY DIVIDED SOLID MATERIAL IN A QUANTITY AND AT A TEMPERATURE SUFFICIENT TO EFFECT COMPLETE VAPORIZATION THEREOF, AND THEN REACTING THE NITRIC ACID VAPOR THUS PRODUCED WITH THE HYDROCARBON REACTANT. 